Slipper



FIG. 1 is a perspective view of a slipper, showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof, and

FIG. 4 is a bottom view of the slipper of FIG. 1. 

The ornamental design for a slipper, substantially as shown and described. 